Motor learning, and transfer in PD and cerebellar dysfunction fundamental to improving the quality of life in Parkinson and cerebellar patients, is deriving approaches that improve their motor capabilities. This requires a better understanding of the extent to which training can enhance their ability to perform certain motor behaviors, and whether those skills can be retained and transferred. The proposed paradigm attempts to integrate motor systems neurobiology with principles that relate therapeutic intervention to specific neurological disorders. The purpose of this research is to examine motor learning of 4 different motor skills in patients with Parkinson's disease and cerebellar dysfunction given extensive practice (2x/day, 5x/week for 4 weeks). The three specific aims for this project are: 1) to measure changes in performance with practice; 2) retention of performance across weeks; and 3) transfer of performance to related skills. Four fundamentally different motor skills will be practiced: a sensory-driven task (intercepting a moving ball); an aiming task (moving rapidly to small and large targets); a repetitive context-driven sequencing task (buttoning); and an internally generated sequencing task (using sign language to spell words). Performance and degree to which the skill is automated will be measured after every 2 hours of practice, and retention will be measured at 5 intervals: 3 days, 1 week, 2 weeks, 1 month and 2 months. In addition, transfer to a related task will be examined. Movement times and kinematics of the movements will be measured, such as trajectory of the movement, jerk (smoothness of movement), velocity and spatial variability. In addition, for the sequential tasks, order of sequence elements, pauses between elements, and relative timing of the elements will be measured. The results will provide foundational data for studying the effect of extensive practice in these clinical groups, insight into the role of the basal ganglia and the cerebellum in learning motor skills, and guidance for improved treatment for PD and cerebellar patients through physical activity and therapy.